Raise helpful exception for requested_schema programming errors.

Author: anthony-tuininga

doc/src/release_notes.rst

@@ -42,6 +42,13 @@ Common Changes
 #)  Updated the `Jupyter notebook samples <https://github.com/oracle/
     python-oracledb/tree/main/samples/notebooks>`__ to cover recent
     python-oracledb features.
+#)  Error ``DPY-2069: requested schema has {num_schema_columns} columns defined
+    but {num_fetched_columns} columns are being fetched`` is now raised when
+    the number of elements in the ``requested_schema`` parameter to
+    :meth:`Connection.fetch_df_all()` and :meth:`Connection.fetch_df_batches()`
+    doesn't match the number of columns being fetched. Previously this scenario
+    would throw unhelpful execptions or cause a segfault under certain
+    circumstances.
 #)  Error ``DPY-2068: scroll operation is not supported on a non-scrollable
     cursor`` is now raised when using :meth:`Cursor.scroll()` method on a
     non-scrollable cursor.

src/oracledb/errors.py

@@ -292,6 +292,7 @@ def _raise_not_supported(feature: str) -> None:
 ERR_EMPTY_STATEMENT = 2066
 ERR_WRONG_DIRECT_PATH_DATA_TYPE = 2067
 ERR_SCROLL_NOT_SUPPORTED = 2068
+ERR_WRONG_REQUESTED_SCHEMA_LENGTH = 2069
 
 # error numbers that result in NotSupportedError
 ERR_TIME_NOT_SUPPORTED = 3000
@@ -1007,6 +1008,10 @@ def _raise_not_supported(feature: str) -> None:
         'found object of type "{actual_schema}.{actual_name}" when '
         'expecting object of type "{expected_schema}.{expected_name}"'
     ),
+    ERR_WRONG_REQUESTED_SCHEMA_LENGTH: (
+        "requested schema has {num_schema_columns} columns defined but "
+        "{num_fetched_columns} are being fetched"
+    ),
     ERR_WRONG_SCROLL_MODE: (
         "scroll mode must be relative, absolute, first or last"
     ),

src/oracledb/impl/base/cursor.pyx

@@ -326,6 +326,13 @@ cdef class BaseCursorImpl:
         Initializes the fetch variable lists in preparation for creating the
         fetch variables used in fetching rows from the database.
         """
+        cdef ssize_t num_schema_columns
+        if self.schema_impl is not None:
+            num_schema_columns = len(self.schema_impl.child_schemas)
+            if num_schema_columns != num_columns:
+                errors._raise_err(errors.ERR_WRONG_REQUESTED_SCHEMA_LENGTH,
+                                  num_schema_columns=num_schema_columns,
+                                  num_fetched_columns=num_columns)
         self.fetch_metadata = [None] * num_columns
         self.fetch_vars = [None] * num_columns
         self.fetch_var_impls = [None] * num_columns

tests/test_9300_dataframe_requested_schema.py

@@ -755,3 +755,28 @@ def test_9327(value, conn, test_env):
         conn.fetch_df_all(
             "select :1 from dual", [value], requested_schema=requested_schema
         )
+
+
+@pytest.mark.parametrize("num_elements", [1, 3])
+def test_9328(num_elements, conn, test_env):
+    "9328 - fetch_df_all() with wrong requested_schema size"
+    elements = [(f"COL_{i}", pyarrow.string()) for i in range(num_elements)]
+    requested_schema = pyarrow.schema(elements)
+    with test_env.assert_raises_full_code("DPY-2069"):
+        conn.fetch_df_all(
+            "select user, user from dual", requested_schema=requested_schema
+        )
+
+
+@pytest.mark.parametrize("num_elements", [1, 3])
+def test_9329(num_elements, conn, test_env):
+    "9329 - fetch_df_batches() with wrong requested_schema size"
+    elements = [(f"COL_{i}", pyarrow.string()) for i in range(num_elements)]
+    requested_schema = pyarrow.schema(elements)
+    with test_env.assert_raises_full_code("DPY-2069"):
+        list(
+            conn.fetch_df_batches(
+                "select user, user from dual",
+                requested_schema=requested_schema,
+            )
+        )

tests/test_9400_dataframe_requested_schema_async.py

@@ -778,3 +778,26 @@ async def test_9427(value, async_conn, test_env):
         await async_conn.fetch_df_all(
             "select :1 from dual", [value], requested_schema=requested_schema
         )
+
+
+@pytest.mark.parametrize("num_elements", [1, 3])
+async def test_9428(num_elements, async_conn, test_env):
+    "9428 - fetch_df_all() with wrong requested_schema size"
+    elements = [(f"COL_{i}", pyarrow.string()) for i in range(num_elements)]
+    requested_schema = pyarrow.schema(elements)
+    with test_env.assert_raises_full_code("DPY-2069"):
+        await async_conn.fetch_df_all(
+            "select user, user from dual", requested_schema=requested_schema
+        )
+
+
+@pytest.mark.parametrize("num_elements", [1, 3])
+async def test_9429(num_elements, async_conn, test_env):
+    "9429 - fetch_df_batches() with wrong requested_schema size"
+    elements = [(f"COL_{i}", pyarrow.string()) for i in range(num_elements)]
+    requested_schema = pyarrow.schema(elements)
+    with test_env.assert_raises_full_code("DPY-2069"):
+        async for df in async_conn.fetch_df_batches(
+            "select user, user from dual", requested_schema=requested_schema
+        ):
+            pass